Date Published: July 26, 2017
Publisher: Springer Berlin Heidelberg
Author(s): Leszek Borkowski, Anna Sroka-Bartnicka, Izabela Polkowska, Marta Pawlowska, Krzysztof Palka, Emil Zieba, Anna Slosarczyk, Krzysztof Jozwiak, Grazyna Ginalska.
Regeneration of bone defects was promoted by a novel β-glucan/carbonate hydroxyapatite composite and characterized by Raman spectroscopy, microCT and electron microscopy. The elastic biomaterial with an apatite-forming ability was developed for bone tissue engineering and implanted into the critical-size defects of rabbits’ tibiae. The bone repair process was analyzed on non-decalcified bone/implant sections during a 6-month regeneration period. Using spectroscopic methods, we were able to determine the presence of amides, lipids and assign the areas of newly formed bone tissue. Raman spectroscopy was also used to assess the chemical changes in the composite before and after the implantation process. SEM analyses showed the mineralization degree in the defect area and that the gap size decreased significantly. Microscopic images revealed that the implant debris were interconnected to the poorly mineralized inner side of a new bone tissue. Our study demonstrated that the composite may serve as a biocompatible background for collagen ingrowth and exhibits the advantages of applying Raman spectroscopy, SEM and microCT in studying these samples.
The increasing number of accidents, injuries and bone tumours along with developments in medical sciences result in growing demand for bone substitute materials. The global bone grafts and substitutes (BGS) market was valued at US$2358.3 million in 2014 and is expected to reach US$3482.0 million by 2023 according to a new report published by Transparency Market Research . Plenty of scientific reports concerning novel materials appear every year and regard many different aspects such as material properties, scaffold design, host response, implant personalization, use of cells and signalling molecules [2, 3]. Ceramic-polymer composites containing synthetic hydroxyapatite have received much attention because of their advantageous properties such as biocompatibility, adaptation to the shape/size of bone defects, sufficient mechanical strength, non-toxicity and possibility of delivering drugs and macromolecules [4–10].
Figure 2a, b demonstrated irregular shapes of the synthesized CHAP granules and uniform density of the particles among fractions. Composite scaffolds were obtained after addition of β-1,3-glucan, which formed a compact mesh widely adhered to CHAP surface (Fig. 2c). Scaffold microarchitecture shown in Fig. 2d exhibited a high porosity and opened pore structure. SEM images also confirmed a homogenous distribution of granules in the scaffolds. Composite samples exhibited high flexibility, could be compressed or bent and adapted easily to appropriate shapes. The obtained material could be formed into different shapes at the preparation step (using different moulds) and after fabrication using scissors or lancet.Fig. 2MicroCT images of CHAP granules and SEM images presenting structure of CHAP/glucan biocomposite. (a) 0.2–0.3 mm fraction of CHAP granules, (b) 0.4–0.6 mm fraction of CHAP granules, (c) CHAP/glucan composite surface magnified 120× and (d) scaffolds microarchitecture magnified ×500
In this study, we investigated in vivo the bioactivity of β-1,3-glucan/CHAP composite using Raman spectroscopy and different imaging techniques (SEM, microCT). The imaging tools such as optical microscope, SEM and high-resolution microCT showed relevant integration of ceramic-polymer composite material with bone tissue 6 months after implantation. Raman microspectroscopy has been employed to study chemical changes in the composite and material composition in bone. This analytical spectroscopic technique offers the possibility to obtain micro-level spatial resolution and permits the detection of local variations in composition. Based on this technique, bone regeneration in terms of (collagen rich) matrix formation and further mineralization was observed and described. Organic fibrils visible in the newly formed bone and at the bone implant border were assigned to collagen type I based on the spectrum of standard protein. It shows that the composite may serve as a biocompatible background for collagen ingrowth. The mineralization of newly formed bone reflected its maturation which progressed from the edge to the centre of defect area. Raman spectroscopy appeared to be very useful in estimating the degree of mineralization process and maturity of bone tissue. Implant debris were still visible after 6 months and remained inside the marrow cavity. This study leads to the conclusion that CHAP/glucan composite demonstrates bioactive and biocompatible properties for bone repair process.